In the paper industry, paper rolls are packaged in wrappers sealed with end headers. The wrapper sheet conventionally employed is comprised of several layers, frequently in a combination of kraft wrapper-plastic film laminate-kraft wrapper (e.g. Kraftliner 100 g/m.sup.2 +PE 40 g/m.sup.2 +Kraftliner 100 g/m.sup.2). The purpose of the packaging system is to protect the roll against humidity, physical damage and to provide the facility of mechanical handling without damaging the roll itself. Further, two or more small rolls are often packed in a single package, whereby the packaging system must be sufficiently strong to keep the package together.
Suitable packaging is related to several factors. Such factors include efficient initial gluing for achieving a tight wrap and a smooth wrapper surface without wrinkles to keep the wrapper straight and tensioned during roll wrapping. For rolls that must be free from the initial adhesive stripe as defined by customer specification, wrap tension is attained by the use of a guide-about apparatus. The quality of such wrapping remains inferior, however. Successful folding of the wrapper sheet requires correct application of pressure by the crimping arms and proper moisture content (8 . . . 11%) of the wrap. At a correct level of moisture content, the fold becomes sharp and the folded edge remains parallel with the roll end. The moisture content of the wrapper often drops further during storage, whereby the wrapper becomes tight and small wrinkles are smoothed away.
In present methods, the wrapper sheet is often sealed using a hot-melt or cold-setting glue. Gluing takes place by spraying glue stripes onto the wrap, whereby the wrapper is adhered to the roll over the width (3 . . . 5 mm) of the glue stripes. Also known in the art are implementations based on hot-melt gluing that use a wrapping material having a layer of heat-meltable laminate on the wrap. The U.S. Pat. No. 4,716,709, for example, describes the method outlined in the introductory part of this text, in which method the start end and the finish end of the wrapper sheet are sealed to the roll by melting the polyethyene film coat of the wrapping material. The plastic film laminate acts both as a moisture barrier and a glue layer. Melting in accordance with U.S. Pat. No. 4,716,709 takes place with the help of a heater bar which is pressed against the paper layer of the wrap.
A problem in the above described methods is posed by the small area of glue adherence. Having a small area of glue adherence lowers the durability and moisture barrier characteristics of the wrap. When paper rolls are stacked above one another, the highest wear of the wrapper is concentrated to the angle of the wrapper at the corner of the roll end and roll circumference, where a small air pocket (earmark) unavoidably remains. This occurs during the folding of the wrapper at points where the wrapper sheet remains detached from the roll during the wrap-about and consequently does not fold sufficiently sharply parallel to the roll end. Furthermore, both hot-melt and cold glue applicator apparatuses require frequent servicing due to their complicated structure. Therefore, wrapping costs become a dominating factor in the total costs of roll packaging.